<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style type="text/css">
        .container{
            display:flex
        }

        .left{
            width: 100px;
            height: 200px;
            position: relative;
            overflow: hidden;
            background: pink;
        }

        .leftcircle{
            width: 160px;
            height: 160px;
            border: 20px solid white;
            position: absolute;
            border-radius: 50%;
            left: 0px;
            top:0px;
            border-bottom: 20px solid orange;
            border-left: 20px solid orange;
            transform: rotate(45deg);
            animation-name:circle_left;
            animation-duration: 2s;
            animation-timing-function: linear;
            animation-iteration-count: infinite;

        }

        .right {
            width: 100px;
            height: 200px;
            position: relative;
            overflow: hidden;
            background-color: pink;
        }

        .rightcircle {
            width: 160px;
            height: 160px;
            border-radius: 50%;
            border: 20px solid white;
            position: absolute;
            border-top: 20px solid orange;
            border-right: 20px solid orange;
            right: 0px;
            top: 0px;
            animation-name: circle_right;
            animation-duration: 2s;
            animation-timing-function: linear;
            animation-iteration-count: infinite;
            transform: rotate(-135deg);
        }

        @keyframes circle_right {
            0% {
                transform: rotate(-135deg);
            }

            50%,100% {
                transform: rotate(45deg);
            }
        }
        @keyframes circle_left {
            0%,50% {
                transform: rotate(-135deg);
            }

            100% {
                transform: rotate(45deg);
            }
        }
    </style>
</head>

<body>
    <!-- <div class="demo"></div> -->
    <div class='container'>
        <div class="left">
            <div class="leftcircle"></div>
        </div>
        <div class="right">
            <div class="rightcircle"></div>
        </div>
    </div>
</body>

</html>